Hold the set of cards in the palm of your dominant hand with the card backs facing you. Choose any number of cards from a five-card hand to a fifty-two card deck, and hold them all together. Smaller numbers of cards are easier for the beginner.
Apply pressure with your thumb to the outside edge of the card nearest you. This will reveal to your audience the suit or image of that card.
Twist your thumb to apply pressure to the next card in the set. This will take some practice as you must learn to keep the first card from moving while revealing part of the next.
Continue this process for the third card and progress so that each card is revealed in the same style. Once all cards are partially revealed you should have a fan-shaped deck of cards with one corner of each card clearly visible to the audience.
Practice this technique often. It can be hard to get the hang of fanning a deck at first, but it is a very impressive flourish once mastered.